| 摘要 |
<p>PROBLEM TO BE SOLVED: To increase the efficiency of manufacturing a prefabricated concrete duct for a underground line. SOLUTION: Insert holes 14, 31 are made in a base plate mold 11, which forms the face of the female connecting edge of a duct for a underground line, and a top plate mold 30, which forms the face of the female connecting edge. Ring protrusions 15, 32, which forms a chamfering slant face at the opening of the penetrating holes of the pipe for the underground line, are provided above the rim of the opening of the insert hole 14 of the base plate mold and below the rim of the opening of the top plate mold. An internal tube mold 26, which forms the through holes, is structured so as to expand or shrink by the injection or discharging of a liquid. Then, a circumferential mold 16, which forms the circumferential surface of the duct for the underground line, is put on the base plate mold 11 and the top plate mold 30 on it. The internal tube mold 26 is inserted into the insert holes 14, 31 to be positioned inside the circumferential mold 16. After the mold form is assembled, the outside diameter of the internal tube mold 26 is expanded and concrete is injected to fill up the mold form. After the concrete is cured, the molds are detached by shrinking the outside diameter of the internal tube mold 26.</p> |
